Endoscope apparatus

ABSTRACT

An auxiliary measurement light-emitting unit emits auxiliary measurement light that is planar light including at least two first feature lines. A taken image obtained through the imaging of a subject includes an intersection curve and at least two first spots that are formed at positions corresponding to first feature lines on the intersection curve. Measurement information representing the actual size of the subject is displayed in the taken image by using the positions of the first spots.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C § 119(a) to JapanesePatent Application No. 2018-127445 filed on Jul. 4, 2018. The aboveapplication is hereby expressly incorporated by reference, in itsentirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an endoscope apparatus that measuresthe size of a subject.

2. Description of the Related Art

A distance to an object to be observed, the size of an object to beobserved, or the like is acquired in an endoscope apparatus. Forexample, in JP1991-231622A (JP-H03-231622A), a beam is applied to asubject from the distal end portion of an endoscope and a distance to anobject to be observed and the like are calculated from the position andangle of a point of the beam that is formed on the subject by theapplication of the beam. Further, in JP2017-508529A (corresponding toUS2016/287141A1), planar light is applied to a subject to form anintersection curve where the planar light and the subject cross eachother on the subject and a distance between two points on theintersection curve is calculated. Furthermore, in JP2013-005830A, in acase where two illumination windows emitting illumination light areprovided at the distal end portion of an endoscope, two bright spots arcformed on a subject by two pieces of illumination light emitted fromthese two illumination windows and a distance to an object to beobserved is calculated from a distance between the two bright spots.

SUMMARY OF THE INVENTION

Since subjects to be observed by an endoscope in a medical field oftenhave a three-dimensional shape, there is a need for a method ofacquiring measurement information suitable for a three-dimensionalshape. In this regard, since only positional information about one pointbased on a beam is obtained in the JP1991-231622A (JP-H03-231622A), amethod disclosed in JP1991-231622A (JP-H03-231622A) is not suitable forthe acquisition of measurement information in a case where a subject hasa three-dimensional shape.

On the other hand, since a distance is calculated from two points on theintersection curve in JP2017-508529A, a method disclosed inJP2017-508529A is suitable for the acquisition of measurementinformation in a case where a subject has a three-dimensional shape.However, since a user needs to designate two points on the intersectioncurve by a graphical user interface (GUI), the method disclosed inJP2017-508529A is inconvenient in the operation of an endoscope where auser uses both hands. Further, since the intersection curve is alwayschanged, the intersection curve is designated in a static image inJP2017-508529A. For this reason, there is a need for a method formeasuring a distance between two points not in a static image but in amotion picture.

Further, in JP2013-005830A, measurement information in a case where asubject has a three-dimensional shape can be more accurately acquiredusing positional information about a portion between two bright spots.However, since only positional information about two bright spots isobtained in the case of JP2013-005830A, it is difficult to graspinformation about a portion between these two bright spots, for example,the undulation of a subject and the like.

An object of the invention is to provide an endoscope apparatus that cansimply and accurately obtain measurement information without imposing aburden on a user in a case where a subject has a three-dimensionalshape.

An endoscope apparatus according to an aspect of the invention comprisesan auxiliary measurement light-emitting unit that emits auxiliarymeasurement light as planar light including at least two first featurelines, an imaging element that images a subject illuminated with theauxiliary measurement light, an image acquisition unit that acquires ataken image obtained in a case where the subject is imaged by theimaging element, the taken image including an intersection curve formedon the subject and at least two first feature points formed at positionscorresponding to the first feature lines on the intersection curve, aposition specifying unit that specifies at least positions of the firstfeature points on the basis of the taken image, and a display controlunit that displays measurement information representing an actual sizeof the subject in the taken image by using the positions of the firstfeature points.

It is preferable that the measurement information includes a firststraight-line distance between the two first feature points. It ispreferable that the measurement information includes a secondstraight-line distance between one of the two first feature points and aspecific point other than the two first feature points. It is preferablethat the measurement information includes a length of a specificintersection curved portion of the intersection curve positioned betweenthe two first feature points, the position specifying unit specifies aposition of the specific intersection curved portion, and the displaycontrol unit displays the length of the specific intersection curvedportion in the taken image by using the positions of the first featurepoints and the position of the specific intersection curved portion.

It is preferable that the auxiliary measurement light includes aplurality of second feature lines, which are different from the firstfeature lines, between the two first feature lines, the specificintersection curved portion includes a plurality of second featurepoints formed on the intersection curve by the second feature lines soas to be smaller than the first feature points, and the positionspecifying unit specifies the position of the specific intersectioncurved portion from the plurality of second feature points included inthe taken image.

It is preferable that the endoscope apparatus further comprises ameasurement information switching unit that switches the measurementinformation to be displayed in the taken image to any one of a pluralityof pieces of measurement information or a combination of two or more ofa plurality of pieces of measurement information in a case where thereare a plurality of pieces of measurement information. It is preferablethat the endoscope apparatus further comprises a staticimage-acquisition command unit giving a static image-acquisition commandto acquire a static image of the taken image and the measurementinformation is also stored together in a case where the staticimage-acquisition command is given.

It is preferable that the endoscope apparatus further comprises a firstlight source unit emitting illumination light for illuminating thesubject and the auxiliary measurement light-emitting unit includes asecond light source unit provided independently of the first lightsource unit and an auxiliary measurement optical element used to obtainthe auxiliary measurement light from light emitted from the second lightsource unit. It is preferable that the auxiliary measurementlight-emitting unit includes a specific optical member used to emit theauxiliary measurement light toward the subject in a state where anoptical axis of the imaging element and an optical axis of the auxiliarymeasurement light cross each other. It is preferable that the specificoptical member is provided with an anti-reflection portion. It ispreferable that the auxiliary measurement light-emitting unit includesan auxiliary measurement slit used to emit the auxiliary measurementlight toward the subject in a state where an optical axis of the imagingelement and an optical axis of the auxiliary measurement light crosseach other. It is preferable that the second light source unit is alaser light source. It is preferable that a wavelength of light emittedfrom the second light source unit is in the range of 495 nm to 570 nm.

According to the aspect of the invention, it is possible to simply andaccurately obtain measurement information without imposing a burden on auser in a case where a subject has a three-dimensional shape.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the appearance of an endoscope apparatus.

FIG. 2 is a plan view of a distal end portion of an endoscope.

FIG. 3 is a block diagram showing the function of the endoscopeapparatus.

FIG. 4 is a block diagram of an auxiliary measurement light-emittingunit.

FIG. 5 is a diagram illustrating auxiliary measurement light that isemitted from the distal end portion of the endoscope and reaches asubject and includes two first feature lines.

FIG. 6 is a diagram illustrating auxiliary measurement light that isemitted from the distal end portion of the endoscope and reaches asubject and includes two first feature lines and a plurality of secondfeature lines.

FIG. 7 is a diagram illustrating a relationship between the distal endportion of the endoscope and a near end Px, an intermediate vicinity Py,and a far end Pz in a range Rx of an observation distance.

FIG. 8 is a block diagram showing the function of a signal processingunit.

FIG. 9 is a diagram illustrating a first straight-line distance.

FIG. 10 is a diagram illustrating a method of calculating the firststraight-line distance.

FIG. 11 is a diagram illustrating a second straight-line distance.

FIG. 12 is a diagram illustrating the length of a specific intersectioncurve.

FIG. 13 is a diagram illustrating a method of calculating the length ofthe specific intersection curve.

FIG. 14 is a diagram illustrating measurement markers having the shapeof a concentric circle.

FIG. 15 is a diagram illustrating the first straight-line distance andthe second straight-line distance.

FIG. 16 is a diagram illustrating the lengths of the first straight-linedistance, the second straight-line distance, and the specificintersection curve.

FIG. 17 is a diagram illustrating a graph paper-shaped chart that isused to measure a relationship between the position of a spot and thesize of a second measurement marker in a case where an observationdistance corresponds to the near end Px.

FIG. 18 is a diagram illustrating a graph paper-shaped chart that isused to measure a relationship between the position of a spot and thesize of the second measurement marker in a case where an observationdistance corresponds to the far end Pz.

FIG. 19 is a graph showing a relationship between the pixel position ofa spot in an X direction and the number of pixels of the secondmeasurement marker in the X direction.

FIG. 20 is a graph showing a relationship between the pixel position ofa spot in a Y direction and the number of pixels of the secondmeasurement marker in the X direction.

FIG. 21 is a graph showing a relationship between the pixel position ofa spot in the X direction and the number of pixels of the secondmeasurement marker in the Y direction.

FIG. 22 is a graph showing a relationship between the pixel position ofa spot in the Y direction and the number of pixels of the secondmeasurement marker in the Y direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, an endoscope apparatus 10 includes an endoscope 12,a light source device 14, a processor device 16, a monitor 18, and auser interface 19. The endoscope 12 is optically connected to the lightsource device 14, and is electrically connected to the processor device16. The processor device 16 is electrically connected to the monitor 18(display unit) that displays an image. The user interface 19 isconnected to the processor device 16, and is used for various settingoperations and the like for the processor device 16. The user interface19 includes a mouse and the like in addition to a keyboard shown in FIG.1.

The endoscope 12 includes an insertion part 12 a that is to be insertedinto a subject, an operation part 12 b that is provided at a proximalend portion of the insertion part 12 a, and a bendable portion 12 c anda distal end portion 12 d that are provided at a distal end of theinsertion part 12 a. The bendable portion 12 c operates to be bent bythe operation of an angle knob 12 e of the operation part 12 b. Thedistal end portion 12 d is oriented in a desired direction by thebending operation of the bendable portion 12 c.

The endoscope 12 has a normal mode and a length measurement mode, andthese two modes are switched by a mode changeover switch 13 a (modeswitching unit) that is provided on the operation part 12 b of theendoscope 12. The normal mode is a mode where an object to be observedis illuminated with illumination light. In the length measurement mode,an object to be observed is illuminated with illumination light orauxiliary measurement light and measurement information used to measurethe size and the like of the object to be observed is displayed in ataken image obtained through the imaging of the object to be observed.The measurement information of this embodiment represents the actualsize of a subject.

Further, the operation part 12 b of the endoscope 12 is provided with afreeze switch 13 b (static image-acquisition command unit) that is usedto give a static image-acquisition command to acquire the static imageof a taken image. In a case where a user operates the freeze switch 13b, the screen of the monitor 18 is frozen and displayed and an alertsound (for example, “beep”) informing the acquisition of a static imageis generated together. Then, the static images of the taken image, whichare obtained before and after the operation timing of the freeze switch13 b, are stored in a static image storage unit 37 (see FIG. 3) providedin the processor device 16. Furthermore, it is preferable thatmeasurement information to be described later is also stored togetherwith the static image of the taken image in a case where the endoscope12 is set to the length measurement mode. The static image storage unit37 is a storage unit, such as a hard disk or a universal serial bus(USB) memory. In a case where the processor device 16 can be connectedto a network, the static image of the taken image may be stored in astatic image storage server (not shown), which is connected to anetwork, instead of or in addition to the static image storage unit 37.

A static image-acquisition command may be given using an operationdevice other than the freeze switch 13 b. For example, a foot pedal maybe connected to the processor device 16, and a static image-acquisitioncommand may be given in a case where a user operates the foot pedal (notshown) with a foot. A static image-acquisition command may be given by afoot pedal that is used to switch a mode. Further, a gesture recognitionunit (not shown), which recognizes the gestures of a user, may beconnected to the processor device 16, and a static image-acquisitioncommand may be given in a case where the gesture recognition unitrecognizes a specific gesture of a user. The gesture recognition unitmay also be used to switch a mode.

Furthermore, a visual line input unit (not shown), which is providedclose to the monitor 18, may be connected to the processor device 16,and a static image-acquisition command may be given in a case where thevisual line input unit recognizes that a user's visual line is in apredetermined area of the monitor 18 for a predetermined time or longer.Further, a voice recognition unit (not shown) may be connected to theprocessor device 16, and a static image-acquisition command may be givenin a case where the voice recognition unit recognizes a specific voicegenerated by a user. The voice recognition unit may also be used toswitch a mode. Furthermore, an operation panel (not shown), such as atouch panel, may be connected to the processor device 16, and a staticimage-acquisition command may be given in a case where a user makes aspecific operation on the operation panel. The operation panel may alsobe used to switch a mode.

As shown in FIG. 2, the distal end portion of the endoscope 12 has asubstantially circular shape; and is provided with an objective lens 21that is positioned closest to a subject among optical members of animaging optical system of the endoscope 12, an illumination lens 22 thatis used to irradiate the subject with illumination light, an auxiliarymeasurement optical element 23 that is used to illuminate the subjectwith auxiliary measurement light to be described later, an opening 24that allows a treatment tool to protrude toward the subject, and anair/water supply nozzle 25 that is used to supply air and water.

An optical axis Ax of the objective lens 21 extends in a directionperpendicular to the plane of paper. A vertical first direction D1 isorthogonal to the optical axis Ax, and a horizontal second direction D2is orthogonal to the optical axis Ax and the first direction D1. Theobjective lens 21 and the auxiliary measurement optical element 23 arearranged in the first direction D1.

As shown in FIG. 3, the light source device 14 comprises a light sourceunit 26 (first light source unit) and a light source control unit 27.The light source unit 26 generates illumination light that is used toilluminate the subject. Illumination light emitted from the light sourceunit 26 is incident on a light guide 28, and is applied to the subjectthrough the illumination lens 22. In the light source unit 26, a whitelight source emitting white light, a plurality of light sources, whichincludes a white light source and a light source emitting another colorlight (for example, a blue light source emitting blue light), or thelike is used as a light source of illumination light. The light sourcecontrol unit 27 is connected to a system control unit 41 of theprocessor device 16. The light source control unit 27 controls the lightsource unit on the basis of a command output from the system controlunit 41. In a case where the endoscope 12 is set to the normal mode, thelight source control unit 27 controls the light source unit so that thelight source unit emits illumination light. In a case where theendoscope 12 is set to the length measurement mode, the light sourcecontrol unit 27 controls the light source unit so that the light sourceunit emits illumination light and auxiliary measurement light. Speciallight, which has a wavelength in a blue wavelength range between a bluewavelength range and a red wavelength range and has high intensity, maybe used other than white light as the illumination light.

The distal end portion 12 d of the endoscope 12 is provided with anillumination optical system 29 a, an imaging optical system 29 b, and anauxiliary measurement light-emitting unit 30. The illumination opticalsystem 29 a includes the illumination lens 22, and an object to beobserved is irradiated with light, which is emitted from the light guide28, through the illumination lens 22. The imaging optical system 29 bincludes the objective lens 21 and an imaging element 32. Lightreflected from the object to be observed is incident on the imagingelement 32 through the objective lens 21. Accordingly, the reflectedimage of the object to be observed is formed on the imaging element 32.

The imaging element 32 is a color imaging sensor, and takes thereflected image of the subject and outputs image signals. It ispreferable that the imaging element 32 is a charge coupled device (CCD)imaging sensor, a complementary metal-oxide semiconductor (CMOS) imagingsensor, or the like. The imaging element 32 used in the invention is acolor imaging sensor that is used to obtain RGB image signalscorresponding to three colors of R (red), G (green), and B (blue). Theimaging element 32 is controlled by an imaging control unit 33.

The image signals output from the imaging element 32 are transmitted toa CDS/AGC circuit 34. The CDS/AGC circuit 34 performs correlated doublesampling (CDS) or auto gain control (AGC) on the image signals that areanalog signals. The image signals, which have been transmitted throughthe CDS/AGC circuit 34, are converted into digital image signals by ananalog/digital converter (A/D converter) 35. The digital image signals,which have been subjected to A/D conversion, are input to the processordevice 16 through a communication interface (I/F) 36.

The processor device 16 comprises a communication interface (I/F) 38that is connected to the communication I/F of the endoscope 12, a signalprocessing unit 39, a display control unit 40, and a system control unit41. The communication I/F receives the image signals, which aretransmitted from the communication I/F 36 of the endoscope 12, andtransmits the image signals to the signal processing unit 39. A memory,which temporarily stores the image signals received from thecommunication I/F 38, is built in the signal processing unit 39, and thesignal processing unit 39 processes an image signal group, which is aset of the image signals stored in the memory, to generate the takenimage. In a case where the endoscope 12 is set to the length measurementmode, the signal processing unit 39 may be adapted to performstructure-enhancement processing for enhancing structures, such as bloodvessels, or color difference-enhancement processing for increasing acolor difference between a normal area and a specific area, such as alesion area, of the object to be observed on the taken image.

The display control unit 40 displays the taken image, which is generatedby the signal processing unit 39, on the monitor 18. The system controlunit 41 controls the imaging element 32 through the imaging control unit33 that is provided in the endoscope 12. The imaging control unit 33also controls the CDS/AGC circuit 34 and the A/D converter 35 accordingto the control of the imaging element 32. Further, the system controlunit 41 controls the light source unit 26 through the light sourcecontrol unit 27. Furthermore, the system control unit 41 controls alight source 30 a (see FIG. 4) of the auxiliary measurementlight-emitting unit 30.

As shown in FIG. 4, the auxiliary measurement light-emitting unit 30comprises a light source 30 a, a prism 30 c, and the auxiliarymeasurement optical element 23. The light source 30 a (second lightsource unit) is to emit light having a color that can be detected bypixels of the imaging element 32 (specifically visible light), andincludes a light-emitting element, such as a laser diode (LD) or alight-emitting diode (LED), and a condenser lens that condenses lightemitted from the light-emitting element.

The wavelength of light emitted from the light source 30 a is in therange of, for example, 495 nm to 570 nm, but is not limited thereto.Since green light having a wavelength in the range of 495 nm to 570 nmis used, a position specifying unit 50 easily recognizes the positionsof first spots SP1 or second spots SP2 to be described later even thoughthe subject is illuminated with special light. A wavelength in the rangeof 600 nm to 650 nm may be used as another wavelength. The light source30 a is controlled by the system control unit 41, and emits light on thebasis of a command output from the system control unit 41.

The prism 30 c (specific optical member) is an optical member that isused to change the travel direction of light emitted from the lightsource 30 a. The prism 30 c changes the travel direction of the lightemitted from the light source 30 a so that the light emitted from thelight source 30 a crosses the visual field of the imaging optical systemincluding the objective lens 21 and lens groups. The subject isirradiated with light, which is emitted from the prism 30 c, through theauxiliary measurement optical element 23. Further, it is preferable thatan anti-reflection (AR) coating (anti-reflection portion) is provided onthe prism 30 c. The reason why the anti-reflection coating is performedas described above is that it is difficult for a position specifyingunit 50 to be described later to recognize the positions of first spotsSP1 or second spots SP2 to be formed on the subject by auxiliarymeasurement light in a case where auxiliary measurement light isreflected without being transmitted through the prism 30 c and a ratioof auxiliary measurement light to be applied to the subject is reduced.

The auxiliary measurement optical element 23 is formed of a diffractiveoptical element (DOE) and converts light, which is emitted from theprism 30 c, into auxiliary measurement light that is used to obtainmeasurement information. The details of the auxiliary measurement lightand the travel direction of the auxiliary measurement light will bedescribed later.

The auxiliary measurement light-emitting unit 30 has only to be capableof emitting auxiliary measurement light toward the visual field of theimaging optical system. For example, the light source 30 a may beprovided in the light source device and light emitted from the lightsource 30 a may be guided to the auxiliary measurement optical element23 by optical fibers. Further, the prism 30 c may not be used and thedirections of the light source 30 a and the auxiliary measurementoptical element 23 may be inclined with respect to the optical axis Axso that auxiliary measurement light is emitted in a direction crossingthe visual field of the imaging optical system. In this case, anauxiliary measurement slit is fainted at the distal end portion 12 d ofthe endoscope so that the auxiliary measurement light is emitted.

As shown in FIG. 5, the auxiliary measurement light is formed of planarlight including at least two first feature lines CL. In a case where thesubject is irradiated with the auxiliary measurement light, anintersection curve CC is formed according to undulations on the subjectand first spots SP1 (first feature points) are formed at positionscorresponding to the two first feature lines CL1 on the intersectioncurve CC, respectively. Measurement information is calculated on thebasis of the positions of the first spots SP1 positioned on the subject.Further, as shown in FIG. 6, the auxiliary measurement light may includea plurality of second feature lines CL2, which are different from thefirst feature lines CL1, between the two first feature lines CL1. In acase where the subject is irradiated with the auxiliary measurementlight including the first feature lines CL1 and the second feature linesCL2, second spots SP2 (second feature points) are formed at positionscorresponding to the plurality of second feature lines CL2,respectively. The second spots SP2 are smaller than the first spots SP1and an interval between the second spots SP2 is short. For this reason,a specific intersection curve SCC is formed on the intersection curve CCby the plurality of second spots SP2. Measurement information iscalculated on the basis of the position of the specific intersectioncurve SCC.

In regard to the travel direction of the auxiliary measurement light,the auxiliary measurement light is emitted in a state where an opticalaxis Lm of the auxiliary measurement light crosses the optical axis Axof the objective lens 21 as shown in FIG. 7. In a case where the subjectcan be observed in a range Rx of an observation distance, it isunderstood that the positions (points where the respective arrows Qx,Qy, and Qz cross the optical axis Ax) of the first spots SP1 or thesecond spots SP2 formed on the subject by the auxiliary measurementlight in imaging ranges (shown by arrows Qx, Qy, and Qz) at a near endPx, an intermediate vicinity Py, and a far end Pz of the range Rx aredifferent from each other. The imaging angle of view of the imagingoptical system is represented by an area between two solid lines 101,and measurement is performed in a central area (an area between twodotted lines 102), in which an aberration is small, of this imagingangle of view.

Since the auxiliary measurement light is emitted in a state where theoptical axis Lm of the auxiliary measurement light crosses the opticalaxis Ax as described above, sensitivity to the movement of the positionof a spot with respect to a change in the observation distance is high.Accordingly, the size of the subject can be measured with high accuracy.Then, the subject illuminated with the auxiliary measurement light isimaged by the imaging element 32, so that the taken image including thefirst spots SP1 or the second spots SP2 is obtained. In the taken image,the positions of the first spots SP1 or the second spots SP2 depends ona relationship between the optical axis Ax of the objective lens 21 andthe optical axis Lm of the auxiliary measurement light and anobservation distance. The number of pixels representing the same actualsize (for example, 5 mm) is increased in the case of a short observationdistance, and the number of pixels representing the same actual size(for example, 5 nm) is reduced in the case of a long observationdistance.

Accordingly, in a case where information representing a relationshipbetween the positions of the first spots SP1 or the second spots SP2 andmeasurement information (the number of pixels) corresponding to theactual size of the subject is stored in advance as described in detailbelow, measurement information can be calculated from the positions ofthe first spots SP1 or the second spots SP2.

As shown in FIG. 8, the signal processing unit 39 of the processordevice 16 includes a position specifying unit 50 and a measurementinformation processing unit 52 to recognize the positions of the firstspots SP1 or the second spots SP2 and to calculate measurementinformation. In a case where the endoscope 12 is set to the lengthmeasurement mode, the taken image including the first spots SP1 or thesecond spots SP2 is input to the signal processing unit 39. The takenimage, which includes the first spots SP1 or the second spots SP2, isacquired by the communication I/F 38 (image acquisition unit).

The position specifying unit 50 specifies the positions of the firstspots SP1 or the second spots SP2 from the taken image. The first spotsSP1 or the second spots SP2 are displayed in the taken image assubstantially circular green areas that include many componentscorresponding to the color of the auxiliary measurement light.Accordingly, the position specifying unit 50 specifies the positions ofthe first spots SP1 or the second spots SP2 from the substantiallycircular green areas. As a method of specifying the positions, forexample, there is a method including binarizing the taken image andspecifying the centers of white portions (pixels where signal strengthis higher than a threshold value for binarization) of the binarizedimage as the positions of the first spots SP1 or the second spots SP2.

The measurement information processing unit 52 calculates measurementinformation from the positions of the first spots SP1 or the secondspots SP2. The calculated measurement information is displayed in thetaken image by the display control unit 40. In a case where themeasurement information is calculated on the basis of the positions ofthe two first spots SP1, measurement information can be accuratelycalculated even though the subject has a three-dimensional shape.Further, since the positions of the two first spots SP1 areautomatically recognized by the processor device 16, a burden is notimposed on a user in acquiring the positions of these two first spotsSP1. Furthermore, even though the position of the intersection curve ischanged due to the movement of the subject, the two first spots SP1 onthe intersection curve are automatically recognized and measurementinformation is calculated on the basis of the result of the recognition.Accordingly, measurement information can be acquired from the motionpicture of the taken image.

As shown in FIG. 9, the measurement information includes a firststraight-line distance that represents a straight-line distance betweentwo first and second spots SP1 and SP2. The measurement informationprocessing unit 52 calculates the first straight-line distance by thefollowing method. As shown in FIG. 10, the measurement informationprocessing unit 52 obtains coordinates (xp1, yp1, zp1), which representthe actual size of the subject at the first spot SP1, on the basis ofthe position of the first spot SP1. Here, coordinates, which areobtained from the coordinates of the position of the first spot SP1 inthe taken image and correspond to the actual size, are obtained as xp1and yp1. A coordinate, which is obtained from the coordinates of theposition of the first spot SP1 and the coordinates of the position of apredetermined specific spot SPk (specific point) and corresponds to theactual size, is obtained as zp1. Likewise, the measurement informationprocessing unit 52 obtains coordinates (xp2, yp2, zp2), which representthe actual size of the subject at the second spot SP2, on the basis ofthe position of the second spots SP2. Further, coordinates, which areobtained from the coordinates of the position of the second spot SP2 inthe taken image and correspond to the actual size, are obtained as xp2and yp2. A coordinate, which is obtained from the coordinates of theposition of the second spot SP2 and the coordinates of the position ofthe predetermined specific spot SPk (specific point) and corresponds tothe actual size, is obtained as zp2. Then, the first straight-linedistance is calculated by the following equation.

First straight-linedistance=((xp2−xp1)²+(yp2−yp1)²+(zp2−zp1)²)^(0.5)  Equation)

The calculated first straight-line distance is displayed in the takenimage as measurement information 60 (“20 mm” in FIG. 9). The specificspot SPk may be displayed on the monitor 18, or may not be displayed.

Furthermore, as shown in FIG. 11, the measurement information includes asecond straight-line distance that represents a straight-line distancebetween one (“SP1” in FIG. 11) of the two first and second spots SP1 andSP2 and the specific spot SPk (specific point). For example, in a casewhere the second straight-line distance between the first spot SP1 andthe specific spot SPk is to be obtained, the measurement informationprocessing unit 52 obtains the coordinate zp1 that is obtained from thecoordinates of the position of the first spot SP1 and the coordinates ofthe position of the predetermined specific spot SPk (specific point) andcorresponds to the actual size. The coordinate zp1 corresponds to thesecond straight-line distance between the first spots SP1 and thespecific spot SPk. The calculated second straight-line distance isdisplayed in the taken image as measurement information 62 (“12 mm” inFIG. 11).

As shown in FIG. 12, the measurement information includes the length ofthe specific intersection curve SCC of the intersection curve CC that ispositioned between the two first and second spots SP1 and SP2. Themeasurement information processing unit 52 calculates the length of thespecific intersection curve SCC by the following method. As shown inFIG. 13, a first straight-line distance between the first spot SP1 and asecond spot SP2(1), which is adjacent to the first spot SP1, on thespecific intersection curve SCC is obtained, and the obtained firststraight-line distance is denoted by SCC(0). Here, a method ofcalculating the first straight-line distance is the same as theabove-mentioned method (the same applies hereinafter). Then, a firststraight-line distance between the second spot SP2(1) and a second spotSP2(2), which is adjacent to the second spot SP2(1), on the specificintersection curve SCC is obtained, and the obtained first straight-linedistance is denoted by SL(1).

A first straight-line distance SCC(3) between a second spot SP2(3) and asecond spot SP2(4), . . . , a first straight-line distance SL(n−1)between a second spot SP2(n−1) and a second spot SP2(n) (n is a naturalnumber of 2 or more) are calculated by the above-mentioned method.Further, a first straight-line distance SL(n) between a second spotSP(n) and a second spot SP, which is adjacent to the second spot SP(n),is calculated. Then, all the obtained first straight-line distancesSL(0), SL(1), SL(n−1), and SL(n) are added together, so that the lengthof the specific intersection curve SCC is calculated. The calculatedlength of the specific intersection curve SCC is displayed in the takenimage as measurement information 64 (“25 mm” in FIG. 12).

As shown in 14, the measurement information includes measurement markersrepresenting the actual size of the subject. For example, measurementmarkers MC, which have centers at the first and second spots SP1 and SP2and have the shape of a concentric circle, are included as themeasurement markers. The measurement markers MC having the shape of aconcentric circle represent that distances from the first and secondspots SP1 and SP2 are 5 mm. The measurement markers are displayed in thetaken image by the display control unit 40. The measurement informationprocessing unit 52 generates the measurement markers on the basis of thepositions of the first and second spots SP1 and SP2. Specifically, themeasurement information processing unit 52 calculates the sizes ofmarkers from the positions of the spots with reference to a marker table54 (see FIG. 8) where a relationship between the positions of spots inthe taken image and measurement markers representing the actual size ofa subject is stored. Then, the measurement information processing unit52 generates measurement markers corresponding to the sizes of themarkers. A method of making the marker table 54 will be described later.A cruciform shape and the like are included as the shape of themeasurement marker in addition to the shape of a concentric circle.

The measurement information processing unit 52 calculates at least oneof the first straight-line distance, the second straight-line distance,the length of the specific intersection curve, or the measurementmarkers, as the measurement information. Further, the display controlunit 40 may display one or a combination of a plurality of pieces amongthe measurement information. In this case, the mode changeover switch 13a (measurement information switching unit) is operated to switch themeasurement information to be displayed in the taken image to any one ofthe plurality of pieces of measurement information or a combination oftwo or more of the plurality of pieces of measurement information. Forexample, it is preferable that measurement information to be displayedin the taken image is switched in the order of the first straight-linedistance→the second straight-line distance→the length of the specificintersection curve→the measurement markers→“a combination of two or moreof the first straight-line distance, the second straight-line distance,the length of the specific intersection curve, and the measurementmarkers” whenever the mode changeover switch 13 a is operated. An orderin which measurement information is to be switched or types to whichmeasurement information is to be switched can be appropriately changedby the operation of the user interface 19.

In a case where a combination of the first straight-line distance andthe second straight-line distance among the plurality of pieces ofmeasurement information is to be displayed, the second straight-linedistance between the first spot SP1 and the specific spot SPk (“12 mm”in FIG. 15) and the second straight-line distance between the secondspot SP2 and the specific spot SPk (“25 mm” in FIG. 15) are displayed inthe taken image in addition to the first straight-line distance betweenthe first spot SP1 and the second spot SP2 (“20 mm” in FIG. 15) as shownin FIG. 15.

Further, in a case where a combination of the first straight-linedistance, the second straight-line distance, and the length of thespecific intersection curve among the plurality of pieces of measurementinformation is to be displayed, the second straight-line distancebetween the first spot SP1 and the specific spot SPk (“12 mm” in FIG.16), the second straight-line distance between the second spot SP2 andthe specific spot SPk (“25 mm” in FIG. 16), and the length of thespecific intersection curve (“25 mm” in FIG. 16) are displayed in thetaken image in addition to the first straight-line distance between thefirst spot SP1 and the second spot SP2 (“20 mm” in FIG. 16) as shown inFIG. 16.

A method of making the marker table 54 will be described below. Arelationship between the position of a spot and the size of a marker canbe obtained through the imaging of a chart where a pattern having theactual size is regularly formed. For example, auxiliary measurementlight is emitted to the chart; a graph paper-shaped chart includinglines (5 mm) having the same size as the actual size or lines (forexample, 1 mm) having a size smaller than the actual size is imagedwhile an observation distance is changed to change the position of aspot; and a relationship between the position of a spot (pixelcoordinates of the spot on the imaging surface of the imaging element32) and the number of pixels corresponding to the actual size (pixelsshowing 5 mm that is the actual size) is acquired.

As shown in FIG. 17, (x1, y1) means the pixel position of a spot SPM inan X direction and a Y direction on the imaging surface of the imagingelement 32 (an upper left point is the origin of a coordinate system).The number of pixels in the X direction, which corresponds to the actualsize of 5 mm, at the position (x1, y1) of the spot SPM is denoted byLx1, and the number of pixels in the Y direction is denoted by Ly1. Thismeasurement is repeated while an observation distance is changed. FIG.18 shows a state where the chart including lines having a size of 5 mmas in FIG. 17 is imaged, but an interval between the lines is narrowsince this state is a state where an observation distance is closer tothe far end than that in the state of FIG. 17. In the state of FIG. 18,the number of pixels in the X direction, which corresponds to the actualsize of 5 mm, at the position (x2, y2) of a spot SPN on the imagingsurface of the imaging element 32 is denoted by Lx2, and the number ofpixels in the Y direction is denoted by Ly2. Then, while an observationdistance is changed, the same measurement as those in FIGS. 17 and 18 isrepeated and the results thereof are plotted. The charts are shown inFIGS. 17 and 18 without consideration for the distortion of theobjective lens 21.

FIG. 19 shows a relationship between the X-coordinate of the position ofa spot and Lx (the number of pixels of a second measurement marker inthe X direction), and FIG. 20 shows a relationship between theY-coordinate of the position of a spot and Lx. Lx is expressed by“Lx=g1(x)” as a function of the position in the X direction from therelationship of FIG. 19, and Lx is expressed by “Lx=g2(y)” as a functionof the position in the Y direction from the relationship of FIG. 20. Thefunctions g1 and g2 can be obtained from the above-mentioned plottedresults by, for example, a least-square method.

The X-coordinate of a spot corresponds to the Y-coordinate of a spot oneto one, and basically the same results are obtained (the same number ofpixels is obtained at the position of the same spot) even though any oneof the function g1 or g2 is used. Accordingly, in a case where the sizeof the second measurement marker is to be calculated, any one of thefunction g1 or g2 may be used and a function of which sensitivity to achange in the number of pixels with respect to a change in position ishigher may be selected from the functions g1 and g2. Further, in a casewhere the values of the functions g1 and g2 are significantly differentfrom each other, it may be determined that “the position of a spotcannot be recognized”.

FIG. 21 shows a relationship between the X-coordinate of the position ofa spot and Ly (the number of pixels in the Y direction), and FIG. 22shows a relationship between the Y-coordinate of the position of a spotand Ly. Ly is expressed by “Ly=h1(x)” as the coordinate of the positionin the X direction from the relationship of FIG. 21, and Ly is expressedby “Ly=h2(y)” as the coordinate of the position in the Y direction fromthe relationship of FIG. 22. Any one of the function h1 or h2 may alsobe used as Ly as in the case of Lx.

The functions g1, g2, h1, and h2 obtained as described above are storedin the marker table in the form of a look-up table. The functions g1 andg2 may be stored in the marker table in the form of a function.

In the embodiment, the hardware structures of processing units, whichperform various kinds of processing, such as the signal processing unit39, the display control unit 40, the system control unit 41, theposition specifying unit 50, and the measurement information processingunit 52, are various processors to be described later. Variousprocessors include: a central processing unit (CPU) that is ageneral-purpose processor functioning as various processing units byexecuting software (program); a programmable logic device (PLD) that isa processor of which the circuit configuration can be changed after themanufacture of a field programmable gate array (FPGA) and the like; adedicated electrical circuit that is a processor having circuitconfiguration designed for exclusive use to perform various kinds ofprocessing; and the like.

One processing unit may be formed of one of these various processors, ormay be formed of a combination of two or more same kind or differentkinds of processors (for example, a plurality of FPGAs or a combinationof a CPU and an FPGA). Further, a plurality of processing units may beformed of one processor. As an example where a plurality of processingunits are formed of one processor, first, there is an aspect where oneprocessor is formed of a combination of one or more CPUs and software soas to be typified by a computer, such as a client or a server, andfunctions as a plurality of processing units. Second, there is an aspectwhere a processor fulfilling the functions of the entire system, whichincludes a plurality of processing units, by one integrated circuit (IC)chip is used so as to be typified by System On Chip (SoC) or the like.In this way, various processing units are formed using one or more ofthe above-mentioned various processors as hardware structures.

In addition, the hardware structures of these various processors aremore specifically electrical circuitry where circuit elements, such assemiconductor elements, are combined.

EXPLANATION OF REFERENCES

-   10: endoscope apparatus-   12: endoscope-   12 a: insertion part-   12 b: operation part-   12 c: bendable portion-   12 d: distal end portion-   12 e: angle knob-   13 a: mode changeover switch-   13 b: freeze switch-   14: light source device-   16: processor device-   18: monitor-   19: user interface-   21: objective lens-   22: illumination lens-   23: auxiliary measurement lens-   24: opening-   25: air/water supply nozzle-   26: light source unit-   27: light source control unit-   28: light guide-   29 a: illumination optical system-   29 b: imaging optical system-   30: auxiliary measurement light-emitting unit-   30 a: light source-   30 c: prism-   32: imaging element-   33: imaging control unit-   34: CDS/AGC circuit-   35: A/D circuit-   36: communication interface (I/F)-   37: static image storage unit-   38: communication interface (I/F)-   39: signal processing unit-   40: display control unit-   41: system control unit-   50: position specifying unit-   52: measurement information processing unit-   53: actual size table-   54: marker table-   SP1: first spot-   SP2: second spot-   SPk: specific spot-   CC: intersection curve-   SCC: specific intersection curve-   MC: measurement marker

What is claimed is:
 1. An endoscope apparatus comprising: an auxiliarymeasurement light-emitting unit that emits auxiliary measurement lightas planar light including at least two first feature lines; an imagingelement that images a subject illuminated with the auxiliary measurementlight; an image acquisition unit that acquires a taken image obtained ina case where the subject is imaged by the imaging element, the takenimage including an intersection curve formed on the subject and at leasttwo first feature points formed at positions corresponding to the firstfeature lines on the intersection curve; a position specifying unit thatspecifies at least positions of the first feature points on the basis ofthe taken image; and a display control unit that displays measurementinformation representing an actual size of the subject in the takenimage by using the positions of the first feature points.
 2. Theendoscope apparatus according to claim 1, wherein the measurementinformation includes a first straight-line distance between the twofirst feature points.
 3. The endoscope apparatus according to claim 1,wherein the measurement information includes a second straight-linedistance between one of the two first feature points and a specificpoint other than the two first feature points.
 4. The endoscopeapparatus according to claim 1, wherein the measurement informationincludes a length of a specific intersection curved portion of theintersection curve positioned between the two first feature points, theposition specifying unit specifies a position of the specificintersection curved portion, and the display control unit displays thelength of the specific intersection curved portion in the taken image byusing the positions of the first feature points and the position of thespecific intersection curved portion.
 5. The endoscope apparatusaccording to claim 4, wherein the auxiliary measurement light includes aplurality of second feature lines, which are different from the firstfeature lines, between the two first feature lines, the specificintersection curved portion includes a plurality of second featurepoints that are formed on the intersection curve by the second featurelines so as to be smaller than the first feature points, and theposition specifying unit specifies the position of the specificintersection curved portion from the plurality of second feature pointsincluded in the taken image.
 6. The endoscope apparatus according toclaim 1, further comprising: a measurement information switching unitthat switches the measurement information to be displayed in the takenimage to any one of a plurality of pieces of measurement information ora combination of two or more of a plurality of pieces of measurementinformation in a case where there are a plurality of pieces ofmeasurement information.
 7. The endoscope apparatus according to claim1, further comprising: a static image-acquisition command unit thatgives a static image-acquisition command to acquire a static image ofthe taken image, wherein the measurement information is also storedtogether in a case where the static image-acquisition command is given.8. The endoscope apparatus according to claim 1, further comprising: afirst light source unit that emits illumination light for illuminatingthe subject, wherein the auxiliary measurement light-emitting unitincludes a second light source unit that is provided independently ofthe first light source unit, and an auxiliary measurement opticalelement that is used to obtain the auxiliary measurement light fromlight emitted from the second light source unit.
 9. The endoscopeapparatus according to claim 8, wherein the auxiliary measurementlight-emitting unit includes a specific optical member that is used toemit the auxiliary measurement light toward the subject in a state wherean optical axis of the imaging element and an optical axis of theauxiliary measurement light cross each other.
 10. The endoscopeapparatus according to claim 9, wherein the specific optical member isprovided with an anti-reflection portion.
 11. The endoscope apparatusaccording to claim 8, wherein the auxiliary measurement light-emittingunit includes an auxiliary measurement slit that is used to emit theauxiliary measurement light toward the subject in a state where anoptical axis of the imaging element and an optical axis of the auxiliarymeasurement light cross each other.
 12. The endoscope apparatusaccording to claim 8, wherein the second light source unit is a laserlight source.
 13. The endoscope apparatus according to claim 12, whereina wavelength of light emitted from the second light source unit is inthe range of 495 nm to 570 nm.